Arguments

The name of the file in which to save the history, or
from which to load it. The path is relative to the current
working directory.

max.show

The maximum number of lines to show. Inf will
give all of the currently available history.

reverse

logical. If true, the lines are shown in reverse
order. Note: this is not useful when there are continuation lines.

pattern

A character string to be matched against the lines of
the history. When supplied, only unique matching lines are shown.

...

Arguments to be passed to grep when doing
the matching.

stamp

A value or vector of values to be written into the history.

prefix

A prefix to apply to each line.

suffix

A suffix to apply to each line.

quiet

If TRUE, suppress printing timestamp to the console.

Details

There are several history mechanisms available for the different R
consoles, which work in similar but not identical ways. There are
separate versions of this help file for Unix and Windows.

The functions described here work on Unix-alikes under the
readline command-line interface but may not otherwise (for
example, in batch use or in an embedded application). Note that R
can be built without readline.

R.app, the console on macOS, has a separate and largely
incompatible history mechanism, which by default uses a file
‘.Rapp.history’ and saves up to 250 entries. These functions are
not currently implemented there.

The readline history mechanism
is controlled by two environment variables: R_HISTSIZE controls
the number of lines that are saved (default 512), and R_HISTFILE
(default ‘.Rhistory’) sets the filename used for the
loading/saving of history if requested at the beginning/end of a
session (but not the default for
loadhistory/savehistory). There is no limit on the
number of lines of history retained during a session, so setting
R_HISTSIZE to a large value has no penalty unless a large file
is actually generated.

These environment variables are read at the time of saving, so can be
altered within a session by the use of Sys.setenv.

Note that readline history library saves files with permission
0600, that is with read/write permission for the user and not
even read permission for any other account.

The timestamp function writes a timestamp (or other message)
into the history and echos it to the console. On platforms that do not
support a history mechanism only the console message is printed.

Note

If you want to save the history at the end of (almost) every
interactive session (even those in which you do not save the
workspace), you can put a call to savehistory() in
.Last. See the examples.

Examples

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## Not run: ## Save the history in the home directory: note that it is not## (by default) read from there but from the current directory.Last <-function()if(interactive())try(savehistory("~/.Rhistory"))## End(Not run)